Vinyl halide resins plasticized with 1-substituted-4-carboalkoxy-2-pyrrolidinone



United States Patent VINYL HALIDE RESINS PLASTICIZED WITH 1 SUBSTITUTED-4- CARBOALKOXY-Z-PYR- ROLIDINONE Charles J. Knuth, Flushing, N. Y.,assignor to Chas. Pfizer & Co., Inc., Brooklyn, N. Y., a corporation ofDelaware No Drawing. Application June 21, 1955,

Serial No. 517,082

3 Claims. (Cl. 260-302) This invention relates to a group of plasticcompositions. In particular these compositions comprise a vinyl resinelastomer and an alkyl ester of a l-substituted-4-carboxy-2-pyrrolidinone as a plasticizer.

This application is a continuation-in-part of my copending application,Serial No. 206,512, filed January 17, 1951, now abandoned. In thatapplication the products disclosed as useful plasticizers for vinylresin elastomers were described as mono-ester, organic-substitutedmono-amides of itaconic acid. It has now been found that these novelcompounds have the structure shown below.

wherein R is a C1 to Ca alkyl group and R is an alkyl, aryl, or aralykylgroup. These compounds are prepared by heating an itaconic acid di-esterwith about an equimolar proportion of a primary amine. In thepreparation of these valuable compounds use of a larger proportion ofamine, say two molecular equivalents, results in the formation of thecorresponding l-substituted-4-carboxamido-2- pyrrolidinone inpredominant amount. Less than one mole of amine to one mole of ester maybe used, in which cases the product will still contain some unreactedester. Therefore, it is advisable to carefully control the ratio of thereactants so that these valuable esters are obtained in maximum yieldand purity. Other methods for preparing these compounds are describedhereinafter. Still others will occur to those skilled in the art.

The reaction is usually carried out by mixing the itaconic ester and theprimary amine and heating the mixture at or near the reflux temperature.This temperature is limited by the boiling point of the most volatilecomponent either reactant or reaction product. For example, whenbutylamine, B. P. 78 C., is used with the di-octyl ester, thetemperature is limited by the boiling point of the amine. In cases wherethe lower itaconic esters such as the methyl, ethyl or propyl esters areused with the long chain amines such as octyl amine, it is sometimesconvenient to distill off the volatile alcohol, i. e. methanol, ethanol,or propanol, as it is formed as a by-product in order to force thereaction to completion at a more rapid rate. If the amine and esterreactants are not naturally miscible, it is convenient to use an organicsolvent system.

By using various combinations of amines and di-esters, it is possible toobtain a wide variety of plasticizers of the type disclosed herein. Forexample, when a given diester, e. g., the dibutyl or dioctyl ester wasused with a variety of primary amines, a series of compounds of theforegoing structure was obtained having the same R group with difierentR groups. Amines that were found to be useful include straight orbranched chain alkyl amines such as methylamine, ethylamine,propylamine, butyl- 7 2,811,496 Patented Oct. 29, 1957 amine,hexylamine, and octylamine; alicyclic amines such as cyclohexylamine,aryl amines such as aniline, toluidine,

' and naphthylamine and aralkyl amines such as benzylamine andphenethylamine. With the lower boiling amines such as methylamine andethylamine it is convenient to carry the reaction out in a pressurevessel or sealed tube. Conversely, use of a single amine with a varietyof di-esters yielded a series wherein R was the same and the R groupswere varied. Various itaconic di-esters have been employed including thedimethyl, dibutyl, dihexyl, and dioctyl esters. It is also useful insome instances to convert one ester into another of a higher boilingalcohol by transesterification. For example,l-octyl-4-carbohexoxy-Z-pyrrolidinone may be prepared by heating1-octyl-4-carbomethoxy-Z-pyrrolidinone with hexanol in the presence of asmall amount of sodium methoxide and distilling the methanol out of thereaction vessel as it is formed. Alternatively the original methylester, or other ester, may be hydrolyzed by heating at about 90-100 withaqueous alkali followed by recovery of the free acid and re-esterifi- .1cation with the desired alcohol.

Various other methods, of course, may be used to prepare these novelcompounds. For example, itaconic acid may be heated with a primary amineto yield a l-substituted-4-carboxy-2-pyrrolidinone which is thenconverted to its esters by methods well known in the art.

It is thought that the formation of the plasticizers used herein fromprimary amines and itaconic di-esters takes place by a stepwise process.First the amine adds to the carbon-carbon double bond of the di-ester toform a secondary amino di-ester. The amino function of this intermediateis then so situated in the molecule that the relatively strainlessfive-membered pyrrolidinone ring may form by intra-molecular reaction ofthe amine function with the appropriate ester function. Thisinterpretation is helpful in designing syntheses for these valuableplastici zing compounds. For example, treatment of itaconic anhydridewith a primary amine yields an itaconic halfacid amide. However, thismaterial fails to cyclize on heating to yield a1-alkyl-4-carboxy-Z-pyrrolidinone intermediate since the amido group istoo weakly basic to cyclize by intramolecular addition to the doublebond of the itaconic acid element. Thus, the itaconic acid element mustbe introduced via an intermediate such as itaconic acid or an esterthereof with which the amide forming reaction is less facile than theaddition reaction.

l-substituted-4-carboalkoxy-2-pyrro-lidinones are indistinguishable fromthe simple uncyclized monoamide monoesters of itaconic acid on the basisof their compositions alone. Thus it was necessary to assign the abovestructure to these unique and valuable compounds on the basis of otherevidence. These materials as obtained above were found to be devoid ofcarbon-carbon unsaturation as evidenced by their failure to react withpotassium permanganate and by their failure to absorb hydrogen in thepresence of a platinum oxide catalyst. Uncyclized monoamide monoesterscontain such an unsaturated linkage. The NH function which one wouldexpect to be present if these materials were simple amides was found tobe absent. Thus these compounds did not show the presence of an activehydrogen atom with lithium aluminum hydride and the characteristic NH-infrared absorption in the 2.86 to 3.03 micron region is absent.Positive controls were obtained in carrying out the above tests withN-octyl itaconic half acid amide prepared from octylamine and itaconicanhydride.

1-substituted-4-carboalkoxy-2-pyrrolidinones are generally stable, highboiling liquids and are particularly useful as plasticizers with vinylresins, that is resins such as polyvinyl chloride and vinylchloride-vinyl acetate copolymers. Plastic compositions of this naturepreferably 3 comprise the resin and the new plasticizer in the relativeproportions of about '50 to 90% resin and 10 to 50% plasticizer.Particularly valuable for such uses are the compounds of this inventionrepresented by the foregoing structural formula wherein R andR' together'contain about twelve carbon atoms.

The following examples are given by way of illustration and are not tobe considered as limiting the invention in any way. In fact, manyapparently widely different embodiments of this invention may be madewithout departing from the spirit and scope thereof. It is to beunderstood that the above inventionis limited only as defined in theappended claims. In the following examples temperatures are given indegree centigrade and pressures in millimeters of mercury.

EXAMPLE I Equimolar portions of the dibutyl itaconate (B. P. 190/60 mm.,n 1.4415, 014 0.99) and n-octylamine were mixed at room temperature.Heat was evolved which carried the internal temperature to 68 C. Whenthe reaction had subsided the mixture was heated at 105-1l5 for fourhours. At the conclusion of the period of heating the butanol which hadbeen produced during the reaction was evaporated at reduced pressure andthe residue distilled in vacuo. The straw colored product 1-octyl-4-carbobutoxy-2-pyrrolidinone, was collected boiling over a shortrange centering at 200 C./ 3 mm. 12 1.4638 in 81% yield.

Analysis calcd. for CrzHznNOs: C, 68.65; H, 10.51; N, 4.71. Found: C,68.54; H, 10.39; N, 4.73.

A small quantity of dark residue remained in the distillation flask atthe completion of distillation. It solidified on cooling and wasrecrystallized fromacetone to yield a white crystalline solid, meltingpoint 70-72". After repeated recrystallization the melting point wasraised to 75-78. This material was found to have the composition ofN-octyl 1-octyl-4-carboxamido-Z-pyrrolidinon'e.

Analysis calcd. for C21H40N2O2: C, 71.54; H, 11.44; N, 7.95. Found: C,71.66; H, 11.46; N, 8.16.

EXAMPLE II A series of 1-substituted-4-carboalkoxyQ-pyrrolidinones wasprepared by variations of the procedure 'described above. The reactiontemperatures ranged between 30 and 175 C. The products were recovered asabove 'by vacuum evaporation of volatile constituents from the 4 EXAMPLEIII A group of plastic compositions of this invention was prepared usingthe compounds of Example II as plas- 5 ticizers. They were compoundedwith a vinyl chloridevinyl acetate copolymer powder in the proportion of40% by weight of the new ester-pyrrolidinone as plasticizer and 60% ofthe resin. This resin was a commercially available material known asVYNW Vinylite. The

elastorners were prepared by conventional means on a 2-roll rubber millheated to about 150 C., and were then subjected to a number of standardtests commonly used to valuate such materials. Their properties werecompared with those of a control, treated in the same manner but usingdioctyl phthalate as the plasticizer.

Properties of the plastic compositions Y O 02R HCH2 Plasticizer Stress 1at Tensile 1 Elong. Shore 5 2 r 100% along. Strength at break second (p.s. i.) (p. s. 1.) point Hardness R R (percent) Test 750 l, 575 305 6001, 685 375 62 575 1, 620 345 62 445 1, 675 405 61 1, 365 2, 710 315 74740 1, 855 335 62 650 1, 700 350 G1 octyl. amyl 650 1, 715 340 62 oct0ctyl 850 1, 910 305 64 dioctyl phthalate 930 2, 190 310 66 (control)ASTM D4l2-41. 2 ASTM D676-46T.

' EXAMPLE IV The remarkably eflieient plastieizing action of 1-octyl-4-carbobutyoxy-Z-pyrrolidinone and 1-butyl-4-carbo-octoxy- 2-pyrrolidinonein resins was further tested at various plasticizer concentrationsvarying between 30% and 40%.

50 The data obtained for these elastomers using VYNW Vinylite as theresin component is tabulated below.

Properties of plastic compositions at various plasticizer I-substi2uted-4-carb0rzlkoxy-2-pyrrolidinones concentrations 0 02B C021?. C!H-CH2 HCH2 032 C 0 H2 $0 l Boiling Point, Retractive SpecificSolubility in R R 0. (mm. Pres- Index (25 C. Gravity Water at 25 0.

sure) Sodium D line) methyl. isopropyL... methyl butyl PlasticizerPlasticizer Stress 1 at Tensile 1 Elong. at Shore 5 a Concentra- 100%elong. Strength break point second tions (p. s. i.) (p. s. i.) (percent)Hardness R R 2, 130 2, 920 200 76 butyl oetyl 950 2, 450 280 69 445 1,675 405 61 30 l, 860 2, 930 260 78 octyl. butyl 35 960 2, 220 310 71 40650 1, 700 350 61 30 2, 3, 240 90 dioctyl phthalate 33. 3 1, 650 2, 860270 81 (control) 37 1, 230 2, 500 300 72 40 930 2, 310 66 45 610 1, 700320 1 ASTM D 412-41. 1 ASTM D 676-461.

The valuable compositions of this invention may be wherein R is a C1 toCa alkyl group and R' is selected used in the preparation of moldingcompounds, extruded from the group consisting of an alkyl group, an'aryl and calendered articles, cloth coatings, lacquers, etc. 20 groupand an aralkyl group, the compound constituting Other ingredients forspecific purposes may also be infrom about 10 to about 50% by weight ofthe composicorporated in these plastic compositions, for example, tion.Q additional plasticizers, solvents, non-solvent diluents, pig- 2. Aplastic composition as claimed in claim 1 wherein ments, fillers,stabilizers, and lubricants may be used. R and R together contain abouttwelve carbon atoms. What is claimed is: 25 3. A plastic composition asclaimed in claim 1 wherein 1. A plastic composition comprising a vinylhalide resin and a compound having the structure the vinyl resin is avinyl chloride resin.

References Cited in the file of this patent 00,3 611-011 UNITED STATESPATENTS 1 t 30 2,295,600 Natelson et a1. Sept. 15, 1942

1. A PLASTIC COMPOSITION CONMPRISING A VINYL HALIDE RESIN AND A COMPOUNDHAVING THE STRUCTURE